7921999 has 2 divisors, whose sum is σ = 7922000. Its totient is φ = 7921998.

The previous prime is 7921987. The next prime is 7922021. The reversal of 7921999 is 9991297.

It is a weak prime.

It is an emirp because it is prime and its reverse (9991297) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 7921999 - 2¹⁹ = 7397711 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (7921909) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3960999 + 3961000.

It is an arithmetic number, because the mean of its divisors is an integer number (3961000).

Almost surely, 2^7921999 is an apocalyptic number.

7921999 is a deficient number, since it is larger than the sum of its proper divisors (1).

7921999 is an equidigital number, since it uses as much as digits as its factorization.

7921999 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 91854, while the sum is 46.

The square root of 7921999 is about 2814.6045903466. The cubic root of 7921999 is about 199.3478675944.

The spelling of 7921999 in words is "seven million, nine hundred twenty-one thousand, nine hundred ninety-nine".